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A giant outburst two years before the core-collapse of a massive star

2007; Nature Portfolio; Volume: 447; Issue: 7146 Linguagem: Inglês

10.1038/nature05825

1476-4687

A. Pastorello, S. J. Smartt, S. Mattila, J. J. Eldridge, D. R. Young, K. Itagaki, H. Yamaoka, H. Navasardyan, S. Valenti, F. Patat, I. Agnoletto, T. Augusteijn, S. Benetti, E. Cappellaro, T. Boles, J. M. Bonnet-Bidaud, M. T. Botticella, F. Bufano, Chen Cao, J. Deng, M. Dennefeld, N. Elias‐Rosa, A. Harutyunyan, F. P. Keenan, T. Iijima, V. Lorenzi, P. A. Mazzali, Xiangcun Meng, S. Nakano, T. B. Nielsen, J. V. Smoker, V. Stanishev, M. Turatto, D. Xu, L. Zampieri,

Stellar, planetary, and galactic studies

When a bright optical transient was discovered in galaxy UGC 4904 in October 2004 the signs were that it was big enough and bright enough to be a supernova. Further work suggested that it was not quite on that scale; but almost exactly two years after its discovery it seems to have exploded in a big way. Supernova SN 2006jc is in exactly the same place in the sky as the earlier optical transient. This is the first time that such a double outburst has been observed. One possibility is that the initial transient was an outburst from a Wolf-Rayet star, a very hot massive star losing mass rapidly. Or the system might be a binary containing a luminous blue variable star that erupted in 2004, followed two years later by a companion Wolf-Rayet star exploding as SN 2006jc. The peculiar Type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. An outburst (similar to that of a luminous blue variable star) of a Wolf–Rayet star could be invoked for the transient, but this would be the first observational evidence of such a phenomenon. Alternatively a massive binary system composed of an LBV which erupted in 2004, and a Wolf–Rayet star exploding as SN 2006jc, could explain the observations. The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars1,2. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient4 that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf–Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60–100 solar masses5, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf–Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf–Rayet star exploding as SN 2006jc, could explain the observations.